The present invention relates generally to the manufacture of semiconductor integrated circuit devices and, more particularly, to an apparatus and method for front side chemical mechanical planarization of semiconductor workpieces.
Many electronic and computer-related products such as semiconductors, hard disks and CD-ROMS require highly polished or planarized surfaces in order to achieve optimum performance. In the semiconductor manufacturing industry, for example, silicon workpieces are used in the manufacture of integrated circuit components and the like. The workpieces are known in the industry as xe2x80x9cwafersxe2x80x9d and typically have a flat, circular disk-like shape. The wafers are initially sliced from a silicon ingot and, thereafter, undergo multiple masking, etching, and layer (e.g., dielectric and conductor) deposition processes to create microelectronic structures and circuitry on the wafers. The surface of a wafer undergoing these processes is typically polished or planarized between processing steps to ensure proper flatness, thereby permitting use of subsequent photolithographic processes for building additional dielectric and metallization layers on the wafer surface.
Accordingly, Chemical Mechanical Planarization or Polishing (CMP) machines have been developed to planarize or polish silicon wafer surfaces to a flat condition suitable for manufacture of integrated circuit components and the like. Existing CMP machines and processes typically utilize a wafer carrier or transport apparatus which is positioned above a polishing pad and configured to receive and hold one or more wafers therein. The carrier apparatus may include multiple heads for holding multiple wafers. In operation, the carrier apparatus is lowered such that the wafers held therein are pressed against the polishing pad while the polishing pad is rotated about its vertical axis. The wafers may also be rotated about their vertical axes and oscillated radically back and forth over the pad surface to improve polishing effectiveness.
Prior art CMP machines of this sort, while adequate in most respects, do have certain drawbacks. One such shortcoming of known CMP machines is a difficulty in achieving uniform pressure distribution across the surface of the wafer as it is pressed against the polishing pad. Attaining a uniform pressure distribution is important in that it fosters consistent and uniform polishing across the entire wafer surface. The difficulty in achieving uniform pressure distribution arises from the fact that the entire surface of the wafer is in contact with the polishing pad during polishing operations. Another drawback, arising from the conventional xe2x80x9cface downxe2x80x9d position that a wafer is held in during polishing, is the difficulty of visually or otherwise monitoring the polishing process for consistency and uniformity.
The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by an apparatus for performing semiconductor planarizing operations. In an exemplary embodiment, the apparatus includes a carrier assembly for maintaining a workpiece therein in a face up orientation. A roller assembly includes a first cylindrical roller and a cylindrical second roller, the first and second rollers being linked to one another through a pair of arms. Each of the first and second rollers may be independently positioned with respect to a horizontal plane, the horizontal plane being substantially parallel to a top surface of the workpiece.
Preferably, each of the pair of arms further includes an elbow, thereby providing a pivot point for each of the pair of arms. The apparatus further includes a first horizontally oriented spindle for mounting the first cylindrical roller thereon, and a second horizontally oriented spindle for mounting the second cylindrical roller thereon. The first and second rollers may each include a polish pad thereon, the polish pad being divided into a plurality of segments. In an alternative embodiment, one of the first and second rollers includes a polish pad mounted thereon and the other includes a brush mounted thereon. The carrier assembly preferably further includes a tray mounted upon a vertically oriented spindle, the tray maintaining the workpiece therein in the face up orientation. An endpoint measuring device is used for measuring a thickness of the workpiece.